Lipid metabolism in leaves from young wheat (Triticum aestivum cv. Hereward) plants grown at two carbon dioxide levels

Lipid synthesis was studied in primary leaves from 7-d-old wheat plants which had been grown at either ambient CO2 concentration (350 mu mol mol(-1)) or elevated CO2 (650 mu mol mol(-1)) by incubating tissue samples with [1-C-14]acetate, Growth at different CO2 concentrations did not affect the total incorporation of radiolabel into lipids but it did influence the relative labelling of individual lipid classes, such as diacylglycerol. The leaf basal segment was also studied separately and growth in an enriched CO2 atmosphere was associated with a dramatic increase (over 6-fold) in diphosphatidylglycerol (cardiolipin) labelling, indicating an increased rate of mitochondrial membrane biogenesis, Immunocytological observations correlated with this metabolic result. Both leaf samples showed significant decreases in pigment and surface wax labelling caused by growth at elevated CO2. Growth at different CO2 concentrations also influenced fatty acid labelling patterns, particularly those of the major labelled membrane lipids of the primary leaf whereby there were changes in their ratios of radiolabelled 16 carbon to 18 carbon fatty acids. Phosphatidylglycerol was characterized, for instance, by increased palmitate labelling after wheat was grown in elevated CO2 concentrations, In contrast, phosphatidylcholine was marked by a dramatic decrease in palmitate labelling but a corresponding increase in labelling of its 18 carbon unsaturated fatty acids, The diacylglycerol fraction showed increased unsaturation of its C18 fatty acids. In addition, changes to the fatty acid moieties from the basal segment lipids were also associated with changes in the amount of labelling of the polyenoic fatty acids of monogalactosyldiacylglycerol. Possible reasons for these changes in lipid labelling are discussed. The data show that growth in elevated atmospheric CO2 concentrations causes significant changes in the metabolism of leaf lipids as well as increasing mitochondrial biogenesis.